Preamplifier recommendations for Sony TA F-7B

I am the proud owner of a Sony TA F7B which I am using as a power, hooked upto a pristine pair of Mordaunt Short System 442's. The source is a Sabre DAC and I am using a Cambridge Audio 640A integrated as a Preamplifier.

The system sounds good, very good infact. I am sure it will take a lot of moollah to match it with todays equipment (beautiful music, faultless pace, perfect tonality, great imaging).

I do however feel the Cambridge Audio is the weak link. Any recommendations on a matching preamplifier?